1. Field of the Invention
The present invention refers to a photoelectric pinfall detection system of the kind in which the pins on a bowling lane are remotly scanned without touching them to detect whether each pin is in an upright position or is fallen. The system according to the invention further includes electronic circuitry to display the result of the scanning, not only after a game has finished, but also during the game.
Modern bowling alleys are equipped with more or less automatically operating pinsetters which do the work that earlier has been done manually by the pin boys. Essentially the pinsetters have to remove fallen pins from the bowling lane and to place a complete set of nine or ten pins in a predetermined arrangement in the region of the end of the bowling lane. Thereby a player is enabled to bowl in the ordinary manner, either to knock down as many pins as possible or selected pins. The ball having been thrown the pinsetter has to remove the fallen pins from the lane; usually this is accomplished by lifting the still standing pins from the lane, removing the fallen pins from the lane and repositioning the lifted pins on the lane again.
It must be born in mind that possibly one or several of the pins might be shifted out of the original position under the influence of the ball or of an adjacent falling pin without falling itself. In accordance with the rule of the game the pinsetter has to put all lifted pins, including those which possibly are shifted out of their original position, back to that former position where they in fact have been standing after the ball had been thrown. Now the player has another throw to knock down the remaining pins by means of a second ball. After this second throw all pins, either still standing or fallen, are removed from the lane and the pinsetter prepares a new game by positioning all ten pins in the correct arrangement at the end of the lane. If all ten pins are knocked down by the first ball, the pinsetter proceeds without delay to prepare a new game.
In the most simple case, the scoring is done visually, i.e. the player counts the number of the standing pins after each ball throw, subtracts that number from ten and makes a note of the result. Of course there is a number of different scoring rules which are well known and which have not to be discussed here.
The disadvantages of such visual scoring of the game results may be summarized as follows:
The pins are standing quite far from the player (appr. 25 meters) and the standing pins in front of the player may obstruct the visibility of pins standing farther behind. Still standing pins in a back row may be overseen easily, especially if such a back row pin stands congruent to a front row pin as seen from the players point of view.
The scoring rules especially of the bowling game are comparatively complicated so that errors in recording and calculating the results may easily occur.
Frequently the results of a game are recorded on a transparent foil or film lying on the illuminated area of an overhead projector. The recorded results are thereby projected in blown up form onto a screen so that all players may see the game results of every player simultaneously. However the considerable difference in light intensity, --very bright illuminated area of the overhead projector, where the results are recorded, versus comparatively low light intensity in the region of the pins being arranged in a 25 meters distance--, greatly stresses the accomodation possibilities of the human eye, leading to a premature fatigue of the players and thereby to errors in recording of the results.
Pinsetters widely used with existing bowling alleys may be equipped with means allowing a partly automated scoring in the following way:
The first ball having been thrown, the pin clamping table of the pinsetter is lowered to a distance of appr. 20 cm above the surface of the bowling lane, whereby still standing pins are grasped by means of especially designed clamping devices related to each pin. Now the standing pins are lifted off the lane as precisely as possible in perpendicular direction to the lane surface and the fallen pins are removed from the lane. Each clamping device is equipped with a sensor, e.g. a mechanical switch, which gives an output signal if a pin has been grasped by the related clamping device; consequently the ocurrence of the output signal may be interpreted such that the related pin has to be considered as "standing pin". The output signals of the clamping devices are fed to a display equipped with a number of indicator lamps, the position thereof corresponding to the position of the pins, and each indicator lamp related to a standing pin will be lit in response to the output signals delivered by said sensing switches. After the second ball having been thrown, all ten pins are repositioned anyway for a new game. The pinsetter thereby removes all pins from the lane, whether fallen or not, to prepare a new game after the second ball. A further lowering of the clamping table to detect the number of still standing pins after the second ball is not performed, but the scoring of the second ball throw must be done visually.
Some of the reasons for proceeding in the above mentioned way are discussed hereinafter, as follows:
As already mentioned hereinbefore, there exists the possibility or danger that some of the pins are displaced in a not foreseeable manner from their initial position without falling, due to the influence of the thrown ball or an adjacent falling pin.
The pinsetter can grasp and clamp only those standing pins which are in their initial position or which are displaced from their initial position but to a limited amount, within a comparatively small region around the initial position. This region of grasping is clearly and definitely defined in the standard specification for the admission of pinsetters. However, if a still standing pin is displaced to a position lying beyond that region, the operation of the pinsetter is interrupted and further operation has to be done manually.
It follows that each scanning operation by means of the sensors in the pinsetter to determine which pins are still standing is disadvantageously time-consuming and therefore expensive. Furthermore, if one or several pins are displaced beyond the above mentioned region, where a pin may be grasped by the pinsetter, a scoring based on the information delivered by the sensors provided in the pinsetter will not be reliable at all, but in most cases incorrect and thereby useless.
2. Prior Art
In an attempt to avoid the above mentioned disadvantages, various pinfall detection devices, even including automatic scoring systems, have been proposed in the prior art. Such devices scan the number of the standing pins after a ball throw and remove the necessity to visually inspect the pins and to manually count the number of pins which have not been knocked down by the ball.
U.S. Pat. No. 3,825,749 for example discloses a photoelectric bowling pin detection device including a light source and a photosensitive element mounted for simultaneous sweep across the pin deck of the lane and a drive motor. The scanner is activated by the passage of a delivered ball past a ball detector. As soon as the sweeping light beam hits the head of a standing pin, a portion of the light beam is reflected back to the photosensitive element. The scanner counts the number of occurrences of detection of the light beam portion reflected by a standing pin and derives therefrom the number of standing pins. A disadvantage of this system is that it does not work satisfactorily in bright ambient light conditions and particularly not, if the heads of the pins are damaged and/or contaminated. Furthermore, if two standing pins are one behind the other one, as seen in the direction of the light beam emitted by the scanner, it is not possible to distinguish between the two pins any longer and these two pins will be interpreted as a single standing pin, which is, of course, incorrect and therefore not desirable at all.
In Swiss Pat. No. 306,671 a pinfall detection system has been disclosed comprising a plurality of light barriers arranged in the region of the position of the pins on the bowling lane. The light beam of each light barrier is interrupted by a related pin as long as the latter is standing at its predetermined position, since the beam emitted by a light transmitter arranged at one edge of the lane cannot be received by a light beam receiver arranged at the opposed edge of the lane. The receivers thereby deliver a positive or a negative output signal, which can be interpreted as the related pin being standing or having knocked down. A first disadvantage of this solution is that a considerable number of transmitters and related receivers has to be provided, i.e. ten in the case of a bowling game, which have to be carefully aligned to each other to ensure proper and reliable operation. A second, probably much more important disadvantage lies in the fact that a pin shifted or removed from its initial position, but still standing, does not cause a beam interruption of the related light barrier anymore; consequently such a still standing pin will be interpreted by this system (incorrectly) as a fallen pin.
A pinfall detection system according to the disclosure of German Patent Publication No. 16 03 014 operates also on the basis of a light beam which is reflected by a standing pin and partially received by a photosensitive receiving element; it shows the same disadvantage as hereinbefore discussed in connection with U.S. Pat. No. 3,825,749. A similar solution is disclosed by U.S. Pat. No. 3,705,722; an elongated flash tube is lowered in a position behind the pins after a ball has been delivered and a flash impulse is sent to the heads of the pins. Each standing pin will cause a reflection of the flash and such reflected light beams will be received by a group of receivers focussed to a group of adjacently positioned pins. The number of received reflection signals will be proportional to the number of pins still standing. This latter solution shows the same disadvantages as well, even if it must be admitted that the influence of damage or contamination of the pin heads should be somewhat less due to the shorter distance between light source, pins and receivers. However if the pins are displaced without falling, a distinction between two congruently positioned pins will not be possible.